/*
 * Copyright (C) 2006 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.util.concurrent;

import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * A ThreadFactory which decorates another ThreadFactory to set a name on each
 * thread created.
 * 
 * @author Kevin Bourrillion
 * @since 2009.09.15 <b>tentative</b>
 */
public class NamingThreadFactory implements ThreadFactory {
    private final ThreadFactory backingFactory;
    private final String format;
    private final AtomicInteger count = new AtomicInteger(0);

    public static final ThreadFactory DEFAULT_FACTORY = Executors
            .defaultThreadFactory();

    /**
     * Creates a new factory that delegates to the default thread factory for
     * thread creation, then uses {@code format} to construct a name for the new
     * thread.
     * 
     * @param format
     *            a {@link String#format(String, Object...)}-compatible format
     *            String, to which a unique integer (0, 1, etc.) will be
     *            supplied as the single parameter. This integer will be unique
     *            to this instance of NamingThreadFactory and will be assigned
     *            sequentially.
     */
    public NamingThreadFactory(String format) {
        this(format, DEFAULT_FACTORY);
    }

    /**
     * Creates a new factory that delegates to {@code backingFactory} for thread
     * creation, then uses {@code format} to construct a name for the new
     * thread.
     * 
     * @param format
     *            a {@link String#format(String, Object...)}-compatible format
     *            String, to which a unique integer (0, 1, etc.) will be
     *            supplied as the single parameter
     * @param backingFactory
     *            the factory that will actually create the threads
     * @throws java.util.IllegalFormatException
     *             if {@code format} is invalid
     */
    public NamingThreadFactory(String format, ThreadFactory backingFactory) {
        this.format = format;
        this.backingFactory = backingFactory;
        makeName(0); // fail fast if format is bad
    }

    public Thread newThread(Runnable r) {
        Thread t = backingFactory.newThread(r);
        t.setName(makeName(count.getAndIncrement()));
        return t;
    }

    private String makeName(int ordinal) {
        return String.format(format, ordinal);
    }
}
